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contributions/lib.geocalc/lib/components/geocalculator.cls.php

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<?php
/**
 * Collection of useful functions related to geo coordinates
 * 
 * @ingroup GeoCalc
 * @author Gerd Riesselmann
 */
class GeoCalculator {
        const R = 6371; // Earth radius in km
        
        /**
         * Calculates distance between to points
         * 
         * @param float $lat1 Latitude of point 1;
         * @param float $lon1 Longitude of point 1;
         * @param float $lat2 Latitude of point 2;
         * @param float $lon2 Longitude of point 2;
         * @return float Distance in km
         */
        public static function distance($lat1, $lon1, $lat2, $lon2) {
                // http://www.movable-type.co.uk/scripts/latlong.html
                $lat1 = deg2rad($lat1);
                $lat2 = deg2rad($lat2);
                $lon1 = deg2rad($lon1);
                $lon2 = deg2rad($lon2);
                
                $dLat = $lat2 - $lat1;
                $dLon = $lon2 - $lon1; 
                $a = 
                        sin($dLat/2) * sin($dLat/2) +
                        cos($lat1) * cos($lat2) * 
                        sin($dLon/2) * sin($dLon/2); 
                $c = 2 * atan2(sqrt($a), sqrt(1-$a)); 
                $d = self::R * $c;
                return $d;
        }
        
        /**
         * Compute bounding box
         * 
         * @param float $lat Latitude
         * @param float $lon Longitude
         * @param float $ns_radius Radius of bound box in north to south direction
         * @param float $we_radius Radius of bound box in west to east direction
         * 
         * @return array Array with two elements 'lat' and 'lon', each containing an array 
         *               with two elements 'min' and 'max 
         */
        public static function bounding_box($lat, $lon, $ns_radius, $we_radius) {
                // http://www.movable-type.co.uk/scripts/latlong-db.html
                $d_lat = rad2deg($ns_radius/self::R);
                $d_lon = rad2deg($we_radius/self::R/cos(deg2rad($lat)));
                
                return array(
                        'lat' => array('min' => $lat - $d_lat, 'max' => $lat + $d_lat),
                        'lon' => array('min' => $lon - $d_lon, 'max' => $lon + $d_lon)
                );
        }

        /**
         * Compute bounding box of given coordinates
         *
         * @code
         * GeoCalculator::bounding_box_of(array(
         *   array('lat' => 50.96951, 'lon' => 7.0446),
         *   array('lat' => 50.92181, 'lon' => 6.9462)
         * );
         * @endcode
         *
         * @static
         * @param $arr_coordinates Array of associative array with keys "lat" and "lon"
         * @return array Array with two elements 'lat' and 'lon', each containing an array
         *               with two elements 'min' and 'max. False if $arr_coordinates is empty
         */
        public static function bounding_box_of($arr_coordinates) {
                $first = array_shift($arr_coordinates);
                if ($first == false) {
                        return false;
                }
                $lat_min = Arr::get_item($first, 'lat', 0.0);
                $lat_max = $lat_min;
                $lon_min = Arr::get_item($first, 'lon', 0.0);
                $lon_max = $lon_min;

                foreach($arr_coordinates as $c) {
                        $lat = Arr::get_item($c, 'lat', 0.0);
                        $lon = Arr::get_item($c, 'lon', 0.0);
                        $lat_min = min($lat_min, $lat);
                        $lat_max = max($lat_max, $lat);
                        $lon_min = min($lon_min, $lon);
                        $lon_max = max($lon_max, $lon);
                }

                return array(
                        'lat' => array('min' => $lat_min, 'max' => $lat_max),
                        'lon' => array('min' => $lon_min, 'max' => $lon_max)
                );
        }
}

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